Charge Transfer Regulation toward Organic Copper Iodides with Tunable and Multiswitchable Full-Color Luminescence

Low-dimensional metal halides (LDMHs) have become promising candidates of perovskite luminescent materials, but continuously adjustable full-color emission in a single LDMH platform remains quite challenging due to poor controllability of the luminescence mechanism. Herein, we performed a solvent-mediated strategy to modify the crystal structure of copper(I)-based LDMHs, realizing tunable full-color emission. Specifically, by using homologous Cs@(18-Crown-6) complexes as cationic structural directing agents, we assembled a series of hybrid copper(I) iodides containing [Cu2I4]2–, α-[Cu4I6]2–, β-[Cu4I6]2–, and [Cu5I6(CH3CN)]− units. Through modifying the configuration and interaction modes of organic–inorganic components to regulate intramolecular charge transfer, these copper(I) halides display adjustable luminescence from blue to red, covering the whole visible region. Detailed studies reveal that different coordination environments and weak Cu···Cu bonds diversify the photophysical processes including metal-to-ligand charge transfer and metal-centered and cluster-centered transitions, which result in tunable luminescence output and quantum yield from 56.5% to 90%. More significantly, the homogeneous composition and abundant structural variability endow this halide family with multimodal reversible luminescence switching in a wide emission color range, which showcases potential applications in solid-state lighting diodes, anticounterfeiting, information security, etc. This work realizes continuously adjustable and switchable full-color emission, promoting the rational structural design of LDMHs to remedy typical perovskites.